Copyright © 2012 Red Hat, Inc. All rights reserved. Important 2026-09-07T09:00:00 389-ds-base: 389-ds-base: heap buffer overflow via SASL wrapped-record length lower-bound underflow in sasl_io_start_packet() 7.5 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H CWE-191

A heap buffer overflow flaw was found in the SASL I/O layer of 389 Directory Server (389-ds-base). In sasl_io_start_packet(), the wrapped-record length read from the wire is validated only against an upper bound. A small wire length (0, 1, or 2) produces an encrypted_buffer_count below the already-consumed encrypted_buffer_offset, causing an unsigned subtraction underflow in sasl_io_read_packet(). PR_Recv is then requested to read approximately 4 GiB into a 1024-byte heap buffer, resulting in a heap buffer overflow with attacker-controlled content. After a successful SASL bind with integrity protection (SSF > 0), a remote authenticated attacker can cause a denial of service or potentially achieve remote code execution. This flaw is distinct from CVE-2026-11774, whose fix only guards against upper-bound overflow.

A heap buffer overflow flaw was found in the SASL I/O layer of 389 Directory Server (389-ds-base). In sasl_io_start_packet(), the wrapped-record length read from the wire is validated only against an upper bound. A small wire length (0, 1, or 2) produces an encrypted_buffer_count below the already-consumed encrypted_buffer_offset, causing an unsigned subtraction underflow in sasl_io_read_packet(). PR_Recv is then requested to read approximately 4 GiB into a 1024-byte heap buffer, resulting in a heap buffer overflow with attacker-controlled content. After a successful SASL bind with integrity protection (SSF > 0), a remote authenticated attacker can cause a denial of service or potentially achieve remote code execution. This flaw is distinct from CVE-2026-11774, whose fix only guards against upper-bound overflow.

Red Hat rates this issue as Important. After a successful SASL bind with integrity protection (SSF > 0), an authenticated attacker can send a SASL wrapped record whose length prefix is unusually small. The SASL I/O layer validates that length only against an upper size limit, so when it computes how many more bytes to read it can underflow and write past the end of its receive buffer with attacker-controlled data. This flaw is independent of CVE-2026-11774, which only rejected near-maximum length values; that fix does not cover the lower-bound case. Deployments that do not negotiate a SASL security layer after bind are not exposed on this path. Red Hat would like to thank Adam Korczynski (Ada Logics), Arthur Chan (Ada Logics), David Korczynski (Ada Logics), and Team (Anthropic) for reporting this issue. Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible. Red Hat Directory Server 11.7 E4S for RHEL 8 2026-09-08T00:00:00Z RHSA-2026:64792 redhat-ds:11-8080020260903102346.f969626e Red Hat Directory Server 11.9 for RHEL 8 2026-09-08T00:00:00Z RHSA-2026:64793 redhat-ds:11-8100020260904171440.37ed7c03 Red Hat Directory Server 12.2 E4S for RHEL 9 2026-09-08T00:00:00Z RHSA-2026:64779 redhat-ds:12-9020020260903155914.1674d574 Red Hat Directory Server 12.4 E4S for RHEL 9 2026-09-08T00:00:00Z RHSA-2026:64780 redhat-ds:12-9040020260903102623.1674d574 Red Hat Enterprise Linux 10 2026-09-08T00:00:00Z RHSA-2026:64785 389-ds-base-0:3.2.0-10.el10_2 Red Hat Enterprise Linux 10.0 Extended Update Support 2026-09-08T00:00:00Z RHSA-2026:64804 389-ds-base-0:3.0.6-21.el10_0 Red Hat Enterprise Linux 7 Extended Lifecycle Support 2026-09-08T00:00:00Z RHSA-2026:64771 389-ds-base-0:1.3.11.1-15.el7_9 Red Hat Enterprise Linux 8 2026-09-08T00:00:00Z RHSA-2026:64791 389-ds:1.4-8100020260904155442.25e700aa Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support 2026-09-08T00:00:00Z RHSA-2026:64789 389-ds:1.4-8040020260901171549.96015a92 Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On 2026-09-08T00:00:00Z RHSA-2026:64789 389-ds:1.4-8040020260901171549.96015a92 Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support 2026-09-08T00:00:00Z RHSA-2026:64790 389-ds:1.4-8060020260901145727.824efc52 Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On 2026-09-08T00:00:00Z RHSA-2026:64790 389-ds:1.4-8060020260901145727.824efc52 Red Hat Enterprise Linux 8.8 Telecommunications Update Service 2026-09-08T00:00:00Z RHSA-2026:64776 389-ds:1.4-8080020260831180218.6dbb3803 Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions 2026-09-08T00:00:00Z RHSA-2026:64776 389-ds:1.4-8080020260831180218.6dbb3803 Red Hat Enterprise Linux 9 2026-09-08T00:00:00Z RHSA-2026:64784 389-ds-base-0:2.8.0-10.el9_8 Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 2026-09-08T00:00:00Z RHSA-2026:64778 389-ds-base-0:2.2.4-22.el9_2 Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions 2026-09-08T00:00:00Z RHSA-2026:64781 389-ds-base-0:2.4.5-29.el9_4 Red Hat Enterprise Linux 9.6 Extended Update Support 2026-09-08T00:00:00Z RHSA-2026:64783 389-ds-base-0:2.6.1-24.el9_6 Red Hat Directory Server 13.2 2026-09-08T00:00:00Z RHSA-2026:65119 dirsrv/dirsrv-container-rhel10:1788851765 Red Hat Directory Server 12 Affected redhat-ds:12/389-ds-base Red Hat Directory Server 13 Not affected 389-ds-base Red Hat Enterprise Linux 6 Not affected 389-ds-base https://www.cve.org/CVERecord?id=CVE-2026-18355 https://nvd.nist.gov/vuln/detail/CVE-2026-18355